Radio

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Notes

Prior to Guglielmo Marconi's invention of the radio in 1896, long-distance communication was carried out either by mail or over miles of cable via telegraph. Marconi's first demonstration of the radiotelegraph transmitted a message just over one mile without the use of wires. Continued improvements increased transmission range to over 200 miles by early 1901, and by the end of the year a single letter ("A") had been transmitted across the Atlantic Ocean. By 1905, many ships were equipped with radiotelegraphs for ship-to-ship and ship-to-land communications, and by 1915 the invention of the three-element vacuum tube, or triode, made it possible to regularly transmit voice messages over the airwaves. Throughout the years, radio has been refined not only for communication, but for detection and ranging (Radar) and astronomy.